Title: Discovery of black dye crystal structure polymorphs: Implications for dye conformational variation in dye-sensitized solar cells

Abstract

Here, we present the discovery of a new crystal structure polymorph (1) and pseudopolymorph (2) of the Black Dye, one of the world’s leading dyes for dye-sensitized solar cells, DSSCs (10.4% device performance efficiency). This reveals that Black Dye molecules can adopt multiple low-energy conformers. This is significant since it challenges existing models of the Black Dye···TiO₂ adsorption process that renders a DSSC working electrode; these have assumed a single molecular conformation that refers to the previously reported Black Dye crystal structure (3). The marked structural differences observed between 1, 2, and 3 make the need for modeling multiple conformations more acute. Additionally, the ordered form of the Black Dye (1) provides a more appropriate depiction of its anionic structure, especially regarding its anchoring group and NCS bonding descriptions. The tendency toward NCS ligand isomerism, evidenced via the disordered form 2, has consequences for electron injection and electron recombination in Black Dye embedded DSSC devices. Dyes 2 and 3 differ primarily by the absence or presence of a solvent of crystallization, respectively; solvent environment effects on the dye are thereby elucidated. This discovery of multiple Black Dye conformers from diffraction, with atomic-level definition, complements recently reported nanoscopic evidence for multiplemore » dye conformations existing at a dye···TiO₂ interface, for a chemically similar DSSC dye; those results emanated from imaging and spectroscopy, but were unresolved at the submolecular level. Taken together, these findings lead to the general notion that multiple dye conformations should be explicitly considered when modeling dye···TiO₂ interfaces in DSSCs, at least for ruthenium-based dye complexes.« less

Authors:

Cole, Jacqueline M. ^[1]; Low, Kian Sing ^[2]; Gong, Yun ^[2]

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+ Show Author Affiliations

1. Univ. of Cambridge, Cambridge (United Kingdom); Argonne National Lab. (ANL), Argonne, IL (United States)
2. Univ. of Cambridge, Cambridge (United Kingdom)

Publication Date:

Tue Nov 24 00:00:00 EST 2015

Research Org.:

Argonne National Laboratory (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1352835

Grant/Contract Number:  

AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 7; Journal Issue: 50; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; black dye; dye-sensitized solar cell; dye···TiO2; multiconformation; polymorph; structure